(1) Field of the Invention
The present invention generally relates to control surfaces and more particularly to an articulated control surface system for creating a curved control surface.
(2) Description of the Prior Art
It is well known that control surface actuator noise as well as flow separation induced noise created by current "rigid" control surfaces are significant sources of unwanted noise on underwater and airborne vehicles. The rigid nature of these control surfaces increases the size of the turbulent wake behind the control surface thereby generating significant flow noise levels. The flow noise is created by two mechanisms: (1) the turbulence directly radiating to the near and far field, and (2) the induced noise due to the turbulent excitation of the control surface and the surrounding structure. The latter causes fin and structure reradiation which is the dominant flow noise source.
A variety of techniques have been used to reduce the amount of noise created by existing electro/mechanical actuators. In general, these efforts have concentrated on balancing and isolating the moving parts and gears as well as providing fixed hydro/aerodynamic fairings. Unfortunately, even in the best designs, prior art electro/mechanical actuator-driven control surfaces suffer from the following drawbacks:
(1) Electro/mechanical, hydraulic or pneumatic activation of the control surface resulting in gear and motor noise;
(2) Significant size and weight of actuators add to the overall size and weight of the vehicle, while the seals and bearings associated with these actuators impose concurrent depth limitations and require precise machining tolerances;
(3) Limited control surface placement possibilities since the control surface must have through-hull drives for electro/mechanical or hydraulic actuator systems;
(4) Control hinge gap interrupting flow over the control surface and causing flow separation; and
(5) Increased shed vorticity and turbulent wake created by the rigid control surface, thereby inducing turbulent excitation of the rigid control surface.
(6) The flow is disturbed in the wake of control surfaces where typical propulsors, i.e. propellers, are located thereby greatly contributing to turbulence ingestion noise.